Protecting coating for covered conductors and method of applying the same



July 12, 1927.

O. A. FREDERICKSON PROTECTING COATING FOR COVERED CONDUCTORS AND METHOD OF APPLYING THE SAME Filed March 22. 1927 2 Sheets-Sheet 1 1,635,829 July 12 1927' o. A. FREDERICKSON PROTECTING COATING FOR COVERED CONDUCTORS AND METHOD OF APPLYING THE SAME Filed March 22, 1927 2 Sheets-Sheet 2 2'2 I '//v VEN TOR ATTORNEY Patented July 12,1927.

OTTO

A. IBEDEBICKBON, OF WETHEBSFIELD, CONNECTICUT, AS SIGNOB TO THE WIRE- IOLD COMPANY, OF HARTFORD, CONNECTICUT, A CORPORATION 01 CONNECTICUT.

miorncrme COATING ron covEnEn connuo'rons AND mrrnon or APPLYING mm am.

Application fled much 22, 1027. semi No. 177,424.

This invention relates to a novel protecting coating for the outer jacket of insulated electrical conductors and flexible conduits, and also to a method of applying such coating. The present application is filed as a continuation in art of the Frederickson application Serial No. 144,379, filed October 26, 1926.

Insulated electrical conductors and cables are usually provided with one or more protecting layers or coverings formed of fibrous substances, such as cotton or other inflammable material, and when these conductors are installed in buildings it is important that they be enclosed in metal conduits or be otherwise protected to reduce the fire hazard.

It has therefore been proposed heretofore to apply a coating of Hallie-retarding compound such as stearin pitch or other suitable fatty acid pitches to the outer surface of such covering of insulated electrical conductors to increase their flame-retarding properties, but these flame-retarding compounds impart to the covering a sticky outer surface that causes the adjacent coils of the covering to stick together when the cable is wound into coils ready for the market. This tendency of the coils to stick together, not only makes the cable hard to uncoil, but is further objectionable since when the stuck coils are forced apart portions of the flame-retarding coating are frequently torn from the cable covering.

To overcome this ditliculty it is now the usual practice to apply powdered mica to the flame-retarding coating of the conductor or cable covering, and while the mica reduces the tendency of the adjacent coils to stick together, it does not entirely correct this difficulty, and is objectionable, because it flakes oll' readily, thus exposing the sticky coating, and furthermore the loose detached flakes of -mica becom scattered over the floor of the building and other objects during installation of the cable. Such treated conductor coverings are opento a further obj ecton in that the sticky nature of the flameret-arding coating makes the cable diilicultto draw through conduits, partitions an floors and around corners during installation. If a covered conductor is subjected to a severe pulling strain during installation the conductor may be stretched or drawn out by the pulling force until the diameter of the conductor wire is reduced to such an extent that it will heat up when carrying the electrical load for which it was designed, thus increasing the danger of fire, and more over such pulling strain may cause the coveriplg itsel to be injured.

aving the foregoing in mind the present invention relates to a protecting flexible coating for the outer jacket of electrical conductors and conduits, and to a method of applying the coating, whereby the outer surface of the jacket is given the desired flamerepelling properties and at the same time is rendered smooth and clean, to the end that the adjacent coils will not stick together,

or the. conductor or its covering be in ured during installation.

In carrying out the present invention the fibrous coverln of an insulated conductor or conduit is given a coating of a flame-retarding compound and over this coating is applied a film of wax-like material such as paraffin, the latter being so applied that there is substantially no mixture of the waxlike material with the flame-retarding compound. As a result of the application of the wax-like material to the sticky flame-retarding compound, a smooth, clean, non-sticky outer surface is imparted to the covering of the insulated conductor or conduit, while the flame-retarding properties of the protecting coating are not appreciably decreased by the presence of the wax-like material. This is due to the fact that the wax material is applied to the coated conductor covering in a thin layer such that there is not sufficient wax material present upon the flame-retarding coating to support combustion, and also to the fact that th wax-material is not mechanically mixed with the flame-retarding material but is ap lied over the flameretarding coating to w ich it adheres.

Thea plication of wax-like material to insulate electric conductors for the purpose of rendering such conductors waterproof is not new and it has been proposed heretofore to immerse insulated conductors in a bath of melted wax or paraffin to cause saturation of the insulation and thereby exclude moisture from the interior of the insulating material, but the application of a wax-like material as a film over a sticky or adhesive flame-retarding coating previously applied to the insulating fibrous covering or conduit to impart a smooth, non sticky exterior surface that '15 flame repeltrical cable the outer jacket of which is pro-' vided with the protecting coating'forming the subject matter of the present invention;

Fig. 2 on an enlarged scale is a transverse sectional view through the cable of Fig. 1;

Fig. 3 is a perspective view of a condult for electrical conductors and is shown as provided with the protecting coating of the present invention;

Fig. 4 is a vertical sectional view through mechanism for saturating the outer covering of an insulated conductor with a moisture proofing liquid;

Fig. 5 is a vertical sectional view through somewhat similar mechanism for applying a flame-retarding coating to the cable that has been rendered moisture proof by the treatment of Fig. 4;

'Fig. 6 is a vertical sectional view through mechanism for applying a thin coating of Wax material to the cable that has been flame-proofed by the treatment of Fig. 5;

Fig. 7 is a diagrammatic view of means for winding a treated insulated conductor into coils ready for the market; and

Fig. 8 is a perspective View of a shipping container for a coiled cable.

The protecting coating forming the subject matter of the present invention may be applied to the outer jacket of an insulated conductor, or it may be applied to a flexible tube for a conductor or to a cable formed of two or more covered conductors, or itmay be employed for still other purposes, but in the present instance of the invention it is shown and will be described as applied to the outer fibrous jacket or covering of an electrical cable. a

The insulated electrical cable illustrated in the drawings is shown as provided with two metallic conductors 10, each of which has an insulating jacket 11 formed of rubber, and about this jacket is placed a covering 12 of fibrous material. Around the covering 12 of each conductor is placed a,

further insulating cover 13 and .the two insulated conductors thus formed are enclosed in an outer jacket 14 of fibrous material. The valleys formed between the insulated conductors have the fillers 15 laid therein to fill up the air space between the conductors and outer jacket.

'to the outer The particular construction of the cable so far described forms -no essential part of the present invention but is illustrated as showing a type of non-metallic sheathed cable that has received the approval of the Underwriters Laboratories. The outer covering or" jacket upon which the coating forming the subject matter of the present invention is applied, may be braided, woven or otherwise constructed.

The conduit illustrated in Fig. 3 is shown as a woven tube constructed of the longitudinally extending warp threads 16 and the. spirally disposed weft threads 17, the warp threads may be formed of thick stifi paper while the weft threads 16 are formed of cotton. However, the particular construction of the conduit forms no essential part of this invention.

While the protectin coating of the present invention is descri ed herein as applied jacket 14 of the cable it will be understood that such coating may be applied to the conduit of Fig. 3, to a single insulated conductor such; as the jacket 12 of the conductor 10, or to various other forms of insulated cables or conductors.

In carrying out the covered e ectrical con uctorsor the conduit is preferably first subjected to a moisture proofing treatment to render the covering or acket of proof. This may be done by drawing the covered conductor or conduit from a suppl reel 18 (see Fig. 4) over a roll 19, and into a tank 20 containing the moisture proofing substance 21 which may be bituminous material, such, for instance, as asphalt, pitch, or the l1ke. This substance should have high penetrating properties that will penetrate into the centre of the strands forming the covering or acket 14, and is preferably applied at a high temperature to cause it to drlveoutthe moisture present in the conductor covering. The tank 20 may be heated by a gas burner 22, and as the treated covered conductor leaves the tank the execess liquid 1s removed therefrom.

This may be done by passing the covered conductor or jacket through a die 24 which may be formed of metal and the bore of wluch is preferably slightly smaller than the conductor covering so that the die will act to squeeze from the conductor covering the excess liquid. This is important r'or if an excess amount of the moisture proofing substance is allowed to remain in the cable it will decrease the efl'ectiveness of the flameretarding coating to be subsequently applied. The treated covered conductor or conduit upon leaving the die 24 is puss-ed several times around the upper drum 25 and lower drum 26 to cool the same and is tin-u wound upon the take-up reel 27 readv tor the flame-repellent treatment.

resent invention the.

the; conductor or conduit water- This second treatment may be conveniently effected b the mechanism shown in Fig. 5 wherein the conductorin the present instance of the invention is led from the reel 28 over a roll 29 into a heated tank 30 containing a flameretarding compound 31 such as stearin pitch or other suitable fatty acid itch later described that is heated by t e burner 22. The flame-retarding compound has less saturating properties than the moisture proofing material 21 and consequently forms a coating upon the covering of the conductor or the conduit over the moisture proofing material, the latter serving as a binder that helps to secure the flame-retarding coating to the covering or conduit;

The thickness of the coating 31 upon the jacket 14 is controlled in the present instance by the size of the die 32 formed of metal or other hard material and through which the cable passes as it leaves the tank 30. This die is given a bore that is slightly larger than the cable passing therethrough, so that a layer or coatin of the fire-retarding compound which is ust thick enough to completely cover and protect the surface of the covered conductor or the conduit is permitted to remain thereon. Other means than the die 32 may be employed to deter mine the thickness of this coating, but the use of a die serves to accurately control the thickness of the-coating and also to smooth or iron the coating material so that it w1ll completely cover t e conductor jacket.

As stated the flame-retarding compound is sticky or adhesive, which makes the treated covered conductor difiic'ult to handle; 1t ma= therefore be guided from the die 32 throng a receptacle 33 containing powdered m1ca. This mica treatment is employed merely for the purpose of reducing the sticky condltion of the cable covering during its manufacture, and 'is not an essential feature of the finished product.

Itis important that the hot flame-retard ing compound 31 applied to the textile cov ering or conduit be cooled prior to the wax or parafiine treatment so that the subse uent application of the wax or paratline wil not cause the same to mix with the flame-retarding compound, because such mixture would impair the fire-repellent properties of the flame-retarding compound.

Stearin pitch is an excellent flame-retard ing compound due to its high melting point that ranges from about 250 to 275 Fahrenheit, and also due to itsproperties of expansion under the application of heat so that it forms protecting blisters upon the surface to which it is applied. Parafiine wax has a much lower melting point about to Fahrenheit, and it is therefore feasible to apply the waxto the stearin pitch at a temperature considerably above the melting moisture proofed covered 4 "tank containin point of the wax but still well below the melting point of the stearin pitch.

The temperature at which the wax-like material is applied to the flame retarding compound should be well above the melting int of the wax-like material to facilitate its a lication in a thin film and cause the wax- 1 e material to enter the interstices of the flame-retarding com ound, but such temperature of the waxli e material should not be sufiiciently high to melt or soften the flame retarding compound to such a degree that might cause the wax-like material and flame-retarding compound to become mechanically mixed, a condition that would materially decrease the flame-retarding properties of the flame-retarding compound.

To properly correlate the temperatures of the flame-retarding compound and Wax-like material for the reasons stated, it is desirable to cool "the coveredconductor orconduit after the application of the flame-retarding compound and prior to treatment of the wax-like material. To this end the pres ent invention in one oi its asp-acts subjects the covered conductor or conduit to a cooling operation following the application of the flame-retarding compound, and as shown in the present instance of the invention the covered conductor or conduit upon leaving the the flame-retarding com- 'pound is passe about a roll 34 immersed or partially so in a bath of powdered mica, and is then carried an appropriate number of times about the spaced rolls 35 and 36, the

latter being preferably, though not necessarily supported in abat-h of cooling liquid, argl upon reaching the desired cooled condi 1011 the covered conductor or conduit may be wound upon a reel 38 preparatory to treatment by the wax-like material.

ICC

The flame-proofed covered conductor or conduit is now ready for the wax treatment which may be effected by drawing it from the reel 39 (Fig; 6) into the heated tank 40 containing "wax-like material, such for example as parafiin, ceresin,.beeswax, ozokerite, Montan wax, carnauba, etc. The wax-like, material 41 is applied to the flame-retarding coating 31 in a melted condition but at a temperature that is sufiiciently below the -melting point of the coating material 31 to prevent the wax material from melting said coating or mixing mechanically to any substantial extent with theflame-repellent coatmg.

. As stated, a primary feature of the invention resides in a covered conductor or conduit having wax like material applied to the important for unless the inflammable wax or paraflin is properly applied so that it does not mix to any substantial extent with the flame-repellent compound it Will seriously impair the flan'ie-reta'rding properties of the coating 31.

As the covered conductor or conduit leaves the tank containing the wax-like material 41, all excess Wax material should be removed so that only a film remains, and vhile various means might be employed to fcmove the excess Wax material, one good construction consists of a die 42 through which the covered conductor or conduit is drawn. This die is made of metal or other hard material and is provided with a bore having the same size or practically the same size as the bore of the die 32. The object in giving both dies 32 and 42 the same size is to cause the latter to iron or force the wax into the interstices of the coating of flame-retarding material without at the same time causing a mixture ofthe two materials. The die 42 is kept hot by the wax carried upwardly by the covered conductor or conduit and this increases its ironing action so that it irons the surface of the flame-retarding coating to increase its smoothness and at the same time forces the Wax into the interstices of the coating to impart to the covered conductor or conduit 14 a smooth, polished surface or slick finish that is not sticky.

This wax treatment improves the outer surface of the covered conductor or conduit in many respects without appreciably effooting the flame retarding properties of the coating 31. As a result of this treatment the covered conductor or conduit is rendeipd non-sticky so that adjacent coils when wound into a package and bound tightly will not stick together even in hot weather, and the powdered mica applied to the cable covering will not flake off since the particles of micathat remain upon the covering when it reaches the die 42 are completely embedded in the cable coating by the pressure of the die. The wax also prevents the flame-retarding coating from oxidizing and adds to the moisture proofing properties of the covered conductor; it also forms a clean, smooth lubricant upon its outer surface that facilitates drawing the cable through conduits and openings during installation.

In order more clearly to indicate in the drawings the successive treatments to which the covered conductor or .conduit is subjected, the upper portion of the cable covering 14 of Fig. 1 is shown as untreated, while a portion near the upper end thereof is shown as treated only with the moisture proofing material 21. The lower half of the cable is shown as provided with the flameretarding coating 31 over a portion of which is applied the wax-like material 41. The

coatings upon the conduit of Fig. 3 are similarly shown.

After the treated covered conductor or conduit leaves the die 42 of Fig. 6 it is and conduits forming the subject matter of the present invention may be produced at a very low cost and possesses as one of its most important advantages the complete elimination of the tendency of adjacent coils of a fire-proofed cable or conduit to stick together. This tendency of the treated coils to stick together has been a continuous source of trouble as it not-only makes the. coils hard to unwind, but frequently causes a section of the flame-repellent coating to be torn from one of the coils as they are forced apart. Through the present invention this difliculty is entirely corrected and adjacent coils will no longer stick together even in the hottest weather.

It will be understood from the foregoing that the wax-like film applied over the stearin pitch or other flame-repellent coating does not penetrate deeply into the surface of the coating and does not mechanically mix with it to any substantial extent or otherwise efi'ect its fire-repellent properties, with the result that the stearin pitch maintains its valuable properties of forming protecting blisters about the cable covering when exposed to high temperatures. These blisters provide a free space between the surface ofthe blisters and the outer jacket formed of textile or other inflammable material to protect the jacket in an effective manner from the action of the flame. When a conductor covering having the slick finish of the resent invention is subjected to the action of a flame the wax or paraflin may melt and drop off the stearin pitch leaving the latter in a substantially pure state to form the protecting blisters above mentioned.

An extremely important feature of the of the ordinary cable becomes ignited fromthe torch the flame is likely to creep along the insulation until it reaches some inflammable structure of the building, whereupon a serious fire may be started. It is impossible for a flame to creep along the covering of a conductor having the flame-repellent slick finish of the present invention.

While stearin pitch is found in practice to form an excellent flame-repellent coating,

other forms of fatty acid pitches may be used with more or less success, such for example as palm-oil pitch, bone-fat pitch, cottonseed-oil pitch, cotton pitch, corn-oil pitch, packing-house pitch, etc, and the flame-retarding coating may also be made.

from various combinations of blown, districal conductors and covered conductor coating to give the latter a non-sticky outer surface. An insulated conductor or conduit formed in accordance with the present invention possesses not only the desired flame retarding and .slick'finish characteristicsas hereinbefore described, but it is flexible and can be bent freely without injury to the flame retarding coating or the film of wax or. paraflin, a condition that enables the conductor to be bent. about obstructions during installation, put up in coils or on reels for shipment and otherwise bent since the flame retarding covering remains pliable and flexible in the finished product.

What is claimed is 1. The method of treatinga fibrous jacket or covering for electrical conductors, which consists of coating such jacket or covering with a flame-retarding compound, and applying to the flame-retarding compound coating a film of wax-like material ata temperature below the melting point of the flame-retarding compounds.

2. The method of treating a fibrous jacket or covering for electrical conductors to protect the jacket or covering from combustion, which consists in coating the jacket or covering with a fire-repellent compound, and applying to the surface of the fire-repellent compound a coating of waxlike material at a temperature above the melting point of the wax-like materialand below the melting' point of the fire repellent compound.

3. The method of treating a fibrous jacket or covering for electrical conductors, which consists in coating the jacket or covering with a heated flame-retarding compound, cooling the flame-'retardingcompound, and applying thereto a covering of waxlikc material at a temperature below the melt ing point of the fire-repellent compound.

4. The method of treating a fibrous acket or covering for electrical conductors, which consists in coating the jacket or covering with a sticky fire-repellent compound, and applying to the sticky surface of the flameretarding compound a film of wax-like ma terial at a temperature below the melting point of the fire-repellent compound to, impart a slick finish to the jacket or covering.

5. The method of treating the outer jacket of an electrical conductor to provide the same with afiame-repellent coating having a slick finish, which consists in applying to the jacket a flame-repellen coating of stearin pitch, then applying melted wax-like material to said coating at a temperature below the melting point of the stearin pitch to form upon the stearin pitch coating a film of wax-like material that renders the coat-- ing non-sticky while maintaining unimpaired its flame-repellent properties.

6."The method of treating the outer fabric jacket of an electrical conductor to protect the same from fire and impart a slick finconduit or tubular fabric formed of fibrous ric a non-adhesive outer surface while maintaining unimpaired its flame-retarding properties.

8. The method of treating a n0n-metallic jacket or covering for electrical conductors, which consists in coating the jacket or coverties of the fire-repellent material.

9. In the art of electrical insulation, a non-metallic jacket or covering for electric conductors having a fire-repellent flexible coating and a film of Wax-like material ap plied over said coating.

10. In the art of electrical insulation, a fibrous jacket or covering for electrical con-. ductors having a coating of flexible and sticky flame-retarding material, and a film of Wax-like material applied to the coating of sticky flame-repellent material.

11. In the art of electrical insulation, a fibrous jacket or covering for electrical conductors having a coating of stearin pitch and a film of Wax-like material applied to the surface of the stearin pitch.

12. A jacket for an electrical conductor formed of fibrous material and having a protecting coating of a flexible and sticky flame-retarding compound and a film of sticky flame-retarding compound and a film of wax-like material over said coating to give a smooth non-sticky outer surface.

14. In the art of electrical insulation, a fibrous jacket or covering for electrical conductors having a coating of flame-retarding fatty acid pitch,-and a film of Wax-like material on the flame-retarding fatty acid pitch to impart a slick non-adhesive surface While maintaing unimpaired the flame-repellent properties of the fatty acid pitch.

15. In the art of electrical insulation, a non-metallic jacket having a protective coating of a bituminous flame-retarding compound, and a film of wax-like material applied to the surface of the bituminous flame-retarding compound.

In testimony whereof, I have signed my name to this specification.

OTTO A. FREDERICKSON. 

